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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- S Y S T E M . A T O M I C _ P R I M I T I V E S --
-- --
-- B o d y --
-- --
-- Copyright (C) 2012-2023, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
package body System.Atomic_Primitives is
--------------------
-- Lock_Free_Read --
--------------------
function Lock_Free_Read (Ptr : Address) return Atomic_Type is
function My_Atomic_Load is new Atomic_Load (Atomic_Type);
begin
if Atomic_Type'Atomic_Always_Lock_Free then
return My_Atomic_Load (Ptr, Acquire);
else
raise Program_Error;
end if;
end Lock_Free_Read;
-------------------------
-- Lock_Free_Try_Write --
-------------------------
function Lock_Free_Try_Write
(Ptr : Address;
Expected : in out Atomic_Type;
Desired : Atomic_Type) return Boolean
is
function My_Atomic_Compare_Exchange is
new Atomic_Compare_Exchange (Atomic_Type);
begin
pragma Annotate (Gnatcheck, Exempt_On, "Improper_Returns",
"early returns for performance");
if Expected /= Desired then
if Atomic_Type'Atomic_Always_Lock_Free then
return My_Atomic_Compare_Exchange (Ptr, Expected'Address, Desired);
else
raise Program_Error;
end if;
end if;
return True;
pragma Annotate (Gnatcheck, Exempt_Off, "Improper_Returns");
end Lock_Free_Try_Write;
end System.Atomic_Primitives;
|
